Issue 36

H. Zhu, Frattura ed Integrità Strutturale, 36 (2016) 191-200; DOI: 10.3221/IGF-ESIS.36.19 192 under stress. Through analyzing the structure form and stress performance of the commonly used steel reinforced concrete beam-column joints as well as factors inducing crack formation, Hierro et al. [8] pointed out the defects existing in the researches carried out by Chinese scholars which concern beam-column joints of steel reinforced concrete. The study carried out by Zhao et al. [9] analyzed the distinction between one-off loading and simulated loading adopted in steel reinforced concrete structure using finite element software, which provides an important basis for the design and construction of modern high-rise building. This study explored the crack formation of steel reinforced concrete structure, clarified the development rules of deformation of steel reinforced concrete structure in different strength grades and deformation rules of steel beam in time-varying structure system, analyzed the major reason leading to the deviation by comparing the measured results with the simulated results, and put forward some suggestions to ensure safe and high-efficient construction. A NALYSIS ON CRACK FORMATION OF STEEL REINFORCED CONCRETE STRUCTURE UNDER STRESS Double-tube structure of reinforced concrete einforced concrete double-tube structure refers to the peripheral frame structure whose middle part is two parallel tubes and includes plain concrete structure, reinforced concrete structure and prestressed concrete structure. Fig. 1 shows the construction drawing of an office building with a reinforced concrete double-tube structure. Figure 1 : Reinforcement drawing of the 4 th floor to the 20 th floor of an office building. Deformation of steel reinforced concrete filled double-tube structure in construction period The first issue is the vertical deformation of steel reinforced concrete filled double-tube structure [10]. Steel reinforced concrete filled double-tube structure is a time-varying structure system. Material performance, structure rigidness, boundary condition and construction load all varies with time. Vertical deformation of components of high-rise steel reinforced concrete filled double-tube structure in construction period mainly includes instantaneous elastic deformation, creep deformation and contraction deformation. Fig. 2 shows the time-varying deformation of concrete. For high-rise structure over 10 layers, the effect of vertical deformation needs to be given special consideration. The difference of vertical deformation would make beam or plate to generate additional bending moment and shearing force. If no measures adopt, the component is prone to crack during construction and even induce accidents and result in personal casualty. The second issue is about the horizontal deformation of steel reinforced concrete filled double-tube structure [11]. Compared to the vertical deformation, the horizontal deformation of steel reinforced concrete filled double-tube structure is less outstanding. In construction period, some destabilizing factors may exist under horizontal load as elasticity modulus of concrete materials has not reached the designed value and moreover internal and external tubes have not formed complete coordinated lateral resistant system along with steel framework. R